Devices for monitoring radioactivity have broad utilization in a variety of governmental, industrial, and scientific applications. Monitoring devices may, for example, be employed for environmental applications as well as national security programs. In environmental applications, for example, monitoring devices may be employed to monitor ground water quality or measure and track isotope plumes at nuclear power stations and Department of Energy facilities. For national security programs, monitoring devices may be employed in programs tasked with nuclear non-proliferation detection and monitoring.
Some of these activities cannot conventionally be carried out with monitoring equipment positioned at the specific location to be monitored. Instead, conventional monitoring techniques generally include physically collecting samples at the specific location and transporting the samples to analytical laboratories where lengthy and expensive separation procedures are performed. For example, in order to monitor ground and surface water for specific radionuclides having relatively long to moderate half-lives such as the isotopes strontium-90 (Sr-90) and technetium-99 (Tc-99), which decay by pure beta particle emission and do not release any measurable gamma or X-rays, samples from the water sources must be collected and transported to a remote testing facility. This kind of monitoring for ground and surface water locations typically occurs at frequencies ranging from monthly to yearly, depending on the location of the water wells and the contamination levels. Furthermore, the collection of the necessary physical samples from remote locations is often difficult when weather conditions such as snow and rain make physically reaching the wells dangerous and/or difficult.
One type of conventional radioactivity detection system includes a flow-through detector that continuously monitors the radiation from samples flowing through a cell. Some of these systems require that the solution to be monitored must include or be mixed with a liquid scintillation fluid. Decay events excite the liquid scintillation fluid to produce light, which can then be detected and measured. However, relatively large amounts of scintillation fluid must be used for the system to work accurately and the mixture must then be safely disposed.
Radioactivity detection systems exist that eliminate the need for a scintillation fluid. Such systems employ the use of an insoluble scintillator over which the fluid being tested may flow. However, such systems may not be accurate in detecting an amount of radioactivity in the sample fluid.